Numerical Design and Thermal-Structural Simulation of a Solar-Powered Rotary Kiln for Cushuro (Nostoc sphaericum) Drying

Cushuro (Nostoc sphaericum) is an Andean cyanobacterium of high nutritional value whose processing for flour production faces limitations due to lack of access to electricity in rural areas. Particularly, the drying process compromises hygiene and efficiency, as production is neither continuous nor controlled due to this energy deficiency. This study presents the design and analysis, using structural and thermal numerical simulations in ANSYS Workbench, of a solar thermal rotary kiln with parabolic concentrator, aimed at efficient drying of Cushuro without reliance on external electrical sources. The system uses a set of parabolic mirrors that concentrate solar radiation on a rotating multilayer cylindrical tube, consisting of a stainless steel structure (2 mm thickness), mineral wool as thermal insulation (33.5 mm thickness), and galvanized sheet as external covering (2 mm thickness). In ANSYS, steady-state thermal and structural analyses were performed with real boundary conditions (irradiance of 850 Wm-2), simulating radial heat transfer, internal temperature distributions, thermal gradients, and total system resistance. The results show that the system achieved a stable internal temperature of 90°C, optimal for preserving the product's nutritional properties. A maximum thermal gradient of 5260° C m-1 was reached radially, without compromising the structural integrity. Moreover, the rotation of the tube ensured homogeneous heat distribution, enabling uniform drying of the biomass. This proposal represents an autonomous, sustainable, and replicable solution for rural communities without grid access, promoting decentralized agroindustrial development and renewable energy utilization.